In order to make an accordion envelope, you will need the following: 6 envelopes, 4 pieces of 6x4 1/8 card stock, double sided tape, chalk, a square punch, and glue.
To begin, lay one envelope down on a flat surface, with the envelope opening facing up. Open the mouth of the envelope. Place another envelope on the lip of that envelope. Glue it in place. Then, open the mouth of that envelope. Place another on the lip of that envelope. Repeat. When you get to the last envelope, tuck it's mouth inside of the envelope, taping it down with double sided tape.
Next, chalk the edges of you decorated card stock. Decorate it in a style you choose. Then, tuck the cards into the envelopes.